全文获取类型
收费全文 | 2336篇 |
免费 | 9篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 161篇 |
金属工艺 | 23篇 |
机械仪表 | 15篇 |
建筑科学 | 26篇 |
矿业工程 | 10篇 |
能源动力 | 12篇 |
轻工业 | 24篇 |
水利工程 | 18篇 |
石油天然气 | 71篇 |
无线电 | 73篇 |
一般工业技术 | 127篇 |
冶金工业 | 1589篇 |
原子能技术 | 18篇 |
自动化技术 | 164篇 |
出版年
2014年 | 9篇 |
2013年 | 30篇 |
2012年 | 20篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 23篇 |
2008年 | 18篇 |
2007年 | 29篇 |
2006年 | 26篇 |
2005年 | 16篇 |
2004年 | 11篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 49篇 |
1998年 | 377篇 |
1997年 | 263篇 |
1996年 | 175篇 |
1995年 | 118篇 |
1994年 | 92篇 |
1993年 | 109篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 34篇 |
1989年 | 39篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 42篇 |
1985年 | 33篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1978年 | 13篇 |
1977年 | 79篇 |
1976年 | 123篇 |
1975年 | 10篇 |
1974年 | 21篇 |
1973年 | 27篇 |
1972年 | 11篇 |
1971年 | 19篇 |
1970年 | 18篇 |
1969年 | 17篇 |
1968年 | 10篇 |
1967年 | 8篇 |
1966年 | 11篇 |
1965年 | 11篇 |
排序方式: 共有2345条查询结果,搜索用时 146 毫秒
1.
Magnetic resonance imaging of the pediatric airway 总被引:1,自引:0,他引:1
FL Rimell AM Shapiro MP Meza S Goldman S Hite B Newman 《Canadian Metallurgical Quarterly》1997,123(9):999-1003
2.
Graefe G. Linville A. Shapiro L.D. 《Knowledge and Data Engineering, IEEE Transactions on》1994,6(6):934-944
Efficient algorithms for processing large volumes of data are very important both for relational and new object-oriented database systems. Many query-processing operations can be implemented using sort- or hash-based algorithms, e.g. intersections, joins, and duplicate elimination. In the early relational database systems, only sort-based algorithms were employed. In the last decade, hash-based algorithms have gained acceptance and popularity, and are often considered generally superior to sort-based algorithms such as merge-join. In this article, we compare the concepts behind sort- and hash-based query-processing algorithms and conclude that (1) many dualities exist between the two types of algorithms, (2) their costs differ mostly by percentages rather than by factors, (3) several special cases exist that favor one or the other choice, and (4) there is a strong reason why both hash- and sort-based algorithms should be available in a query-processing system. Our conclusions are supported by experiments performed using the Volcano query execution engine 相似文献
3.
F Jónsson P Madsen LG J?rgensen M Lunding NH Secher 《Canadian Metallurgical Quarterly》1996,158(44):6256-6259
Indices of fluid balance were evaluated during and after aortic surgery in 16 consecutive patients. Thoracic electrical impedance (TI), heart rate (HR), central venous (CVP), pulmonary artery mean (PAMP), pulmonary wedge (PWP) and mean arterial (MAP) pressures as well as fourteen arterial and venous blood gas variables were followed. Consistent with a reduction of TI during the operation, fluid balance was in excess, and it remained elevated on the first postoperative morning. The HR, MAP and PWP remained stable, while CVP and PAMP decreased. Of the determined variables only TI revealed a meaningful correlation to fluid balance (rho = -0.41; p < 0.01). The results indicate that while central venous and pulmonary artery mean pressures gave the impression of a volume deficit, the positive fluid balance was mirrored by thoracic electrical impedance. 相似文献
4.
5.
Roberson Debi; Davidoff Jules; Davies Ian R. L.; Shapiro Laura R. 《Canadian Metallurgical Quarterly》2004,133(4):554
This study unites investigations into the linguistic relativity of color categories with research on children's category acquisition. Naming, comprehension, and memory for colors were tracked in 2 populations over a 3-year period. Children from a seminomadic equatorial African culture, whose language contains 5 color terms, were compared with a group of English children. Despite differences in visual environment, language, and education, they showed similar patterns of term acquisition. Both groups acquired color vocabulary slowly and with great individual variation. Those knowing no color terms made recognition errors based on perceptual distance, and the influence of naming on memory increased with age. An initial perceptually driven color continuum appears to be progressively organized into sets appropriate to each culture and language. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
A Voskova-Goldman A Peier CT Caskey CS Richards LG Shaffer 《Canadian Metallurgical Quarterly》1997,48(6):1633-1638
The challenge of Duchenne muscular dystrophy (DMD) carrier identification resides in the ability to identify the presence of a mutant gene over the background contributed by the normal allele. Current diagnosis of carrier status when a deletion has been identified in a proband is based on an analysis of a gene dosage. We present a diagnostic strategy that uses fluorescence in situ hybridization (FISH) to detect female carriers with major deletions in the dystrophin gene. We screened a human X-chromosome-derived genomic library with a full-length dystrophin cDNA and isolated 15 dystrophin-specific cosmids that contain DMD gene exons. Six cosmids were further tested as FISH probes in control individuals and subsequently applied on chromosomes from eight males with DMD and known deletions and on samples from three female carriers. As expected, X chromosomes in normal females displayed four signals, two for the DMD-specific probe and two for the X-chromosome centromeric probe. Hybridization on chromosomal spreads from carriers of deletions revealed only one signal from the DMD-specific probe and two from the control centromeric probe. Males carrying deletions showed no DMD-specific signal for the deleted exons tested. Our data indicate that FISH could represent an alternative method for the detection of female carriers with DMD gene deletions. 相似文献
7.
8.
A national survey of school psychologists' acceptability of psychological assessment techniques in the area of externalizing problem behaviors was examined. School psychologists' ratings of 2 procedures, Behavioral Assessment (BA) and Traditional Assessment (TA), were compared using an analog case study methodology. Using a random sample of 500 National Association of School Psychologists members from the 1991–1992 membership directory, 339 Ss completed the Assessment Rating Profile after reading a hypothetical case summary describing a student with suspected externalizing problem behaviors. Results indicated statistically significant differences between assessment methods and ratings of acceptability. BA procedures were found to be more acceptable than TA procedures. Implications related to the acceptability of psychological assessment techniques, as well as implications for school psychology practitioners are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
10.
M. A. Abroyan S. L. Kosogorov I. V. Nabokova N. A. Uspenskii V. A. Chumichev V. B. Shapiro V. Ya. Shvedyuk 《Instruments and Experimental Techniques》2007,50(4):530-533
A system for real-time measurements of the current-density distribution in electron beams ejected from large-area electron accelerators has been developed. The system, which is based on Faraday cups, a microprocessor, and a PC, is designed for measuring the parameters of the electron beams ejected from large-area accelerators—devices for ionizing electroionization lasers and technological accelerators—and ensures real-time monitoring of the current-density distribution over the electron-beam cross section with a relative measurement accuracy of at least ±2%. 相似文献